The lens is the most fundamental component of the optical microscope, which is an important instrument of scientific research in a variety of fields, from biology to surface science, to medicine. Until recently, it has been believed that the resolution of any optical instrument built with conventional lenses is limited by the operating wavelength of the light. Such resolution limitations of conventional far-field optics are well known and arise from the wave nature of light. As a result, light cannot be focused beyond the so-called Abbe-Rayleigh limit using conventional optical lenses composed of a homogeneous isotropic medium (E. A. Ash and G. Nicholls, Nature 237, 510-513 (1972); I. I. Smolyaninov, J. Elliot, A. V. Zayats, C. V. Davis, Phys. Rev. Lett. 94, 057401 (2005)).
New forms of optical microscopy have been devised to overcome the diffraction resolution limit. An idea by Synge in 1928 (E. H. Synge, Philos. Mag. 6, 356-362 (1928)) led eventually to the realization of the first near-field scanning optical microscope (NSOM) in 1972 (E. A. Ash and G. Nicholls, Nature 237, 510-513 (1972)), followed by various refinements and variations from the original technique. The common theme to these techniques has been based on collecting the field in very close proximity of the sample by scanning a fiber tip. These new techniques have resulted in much finer resolution beyond the diffraction limitation for an optical instrument and have led to the possibility of resolving details on the 10-100 nm scale.
One of the constraints of NSOM techniques is the need for scanning the sample point by point (or region by region), making the entire procedure relatively slow. Scanning, in principle, prevents NSOM from capturing fast dynamical processes taking place in the sample in real time. In a far-field optical microscope, however, the light scattered or emitted by the sample may be collected by the instrument aperture all at once, making the procedure fast and thus providing the possibility of observing temporally dynamic samples (which is often needed in observing fast dynamic processes in biology and medicine, for example). Far-field optical microscopy, however, uses traditional diffraction-limited optics. Accordingly, there is an urgent need to develop optical microscopy systems and methods that exhibit both high resolution and wide sampling areas.